The present invention relates to a controller for setting a loop length in a flat knitting machine.
As this type of stitch controller for a flat knitting machine, there has been known the one described in, for example, Japanese Examined Patent Application Publication No. 6-94618 previously proposed by the present applicant.
According to this previously proposed stitch controller, as shown in FIG. 6 of the publication, a stitch cam of a carriage that slides on a needle bed to slide a knitting needle forward and backward is operated by oscillating the stitch cam, which is connected to a distal end of an operating lever. The operating lever is oscillated up and down by virtue of a spiral cam groove of a stitch cam operating cam attached to an output shaft of a driving motor. The spiral cam groove of the stitch cam operating cam is configured such that a spacing from a center of the stitch cam operating cam is proportional to a rotational angle of the stitch cam operating cam, and an ascending and descending amount of the stitch cam is also proportional to the rotational angle of the stitch cam operating cam, as indicated by a two-dot chain line B in FIG. 4.
FIG. 1 in the publication shows that the operating lever is oscillated by a stitch cam operating cam equipped with spiral threads.
A loop length available in one knitting machine is roughly decided by a gauge indicating the number of stitches per inch.
For example, in the case of a 16-gauge knitting machine, an interval (pitch) between adjacent needles is 1.5875 mm. In the case of an 8-gauge knitting machine, the pitch between adjacent knitting needles is 3.175 mm.
A sinker is provided between individual knitting needles of a needle bed, and an inter-sinker pitch is equal to an inter-needle pitch.
There are sinkers on both sides of a knitting needle, and a loop length is decided by how far a knitting needle is drawn in by a stitch cam.
Once a gauge is decided, the pitch is decided accordingly. If, therefore, a knitting machine is designed to provide a stitch cam drawn-in amount that exceeds an appropriate range, then sizes of loop length and yarn sizes will not match, thereby making it unsuitable as a product. Thus, only yarns of sizes in a range suited for pitches can be used for making knitted fabrics.
Accordingly, in general knitting machines, drawn-in amounts of stitch cams are set within an appropriate range for gauges. At the gauges, a bottom elastic or the like, for example, is knitted with loops of short length, while plaited patterns, such as a cable-stitch pattern, are knitted with loops of long length.
Recently, however, there has been an increasing demand for xe2x80x9cseamless knitxe2x80x9d that saves a sewing step after a knitting step, and also features improved fashionableness. For making the seamless knit, a tubular sweater having a front body and a back body are joined on sides by a single knitting machine provided with needle beds at its front and back. To respond to demand, seamless knits are made by performing skipped needle knitting in which every other knitting needle of the needle beds are used, with skipped needles being used for transferring stitches to knit the fabric. Skipped-needle knitting is performed as described below.
For example, to knit a seamless sweater by performing skipped-needle knitting using a 16-gauge knitting machine, a pitch between knit stitches will be double a standard pitch. More specifically, a stitch pitch will be 8 gauges, and a drawn-in amount of a stitch cam must be increased to obtain an 8-gauge knit fabric.
The spiral cam groove of the foregoing stitch cam operating cam is designed such that an ascending and descending amount of the stitch cam is proportional to the rotational angle of the stitch cam operating cam. Hence, skipped-needle knitting can be implemented simply by increasing a drawn-in amount; however, there is a problem in that a displacement amount of the stitch cam per step in 16-gauge knitting is basically large, thereby making it impossible to make finer adjustment of loop length.
As a solution, a step motor having a higher resolution could be used as a driving motor, while using the conventional cam design. This, however, leads to a problem of higher manufacturing cost because a step motor is expensive.
Especially, a cam assembly of a knitting machine uses many driving motors. For instance, in a 3-cam knitting machine for making three courses by one travel of a carriage over a needle bed, right and left step motors are provided for one knitting unit, meaning that 3 cams xc3x97 two (right and left) xc3x97 front and rear carriages =12 step motors being necessary. The knitting machine described in the above publication would require six step motors as well as drivers therefor.
The present invention has been proposed in view of the above problems, and it is an object of the invention to make it possible to provide a loop length controller in a flat knitting machine that permits highly accurate loop length control for knitting with a standard gauge, and also permits satisfactory loop length control in a skipped-needle knitting mode without causing an increase in manufacturing cost.
To fulfill the above object, a loop length controller in a flat knitting machine in accordance with the present invention is designed to set a loop length of a knitting fabric by raising or lowering, via a raising and lowering device, a stitch cam attached to a carriage that slides on a needle bed to slidably operate knitting needles forward and backward, with the raising and lowering device comprising a driving motor and a converting mechanism for converting a rotational motion of the driving motor into ascent and descent of a stitch cam, wherein the converting mechanism is configured such that an ascending and descending amount of the stitch cam with respect to the rotational amount of the driving motor differs between a side for a larger drawing-in amount of knitting needles for loops of longer length and a side for a smaller drawing-in amount of knitting needles for loops of shorter length.
Furthermore, the converting mechanism is equipped with an operating lever having one end thereof pivotally supported by a bottom board and another end thereof connected to a stitch can slidably guided by a raising and lowering slide slot, and a stitch cam operating cam (operating cam) provided on an output shaft of the driving motor, wherein the operating lever has an engaging portion, and the stitch cam operating cam comprises a spiral track that slidably engages with the engaging portion. The track is shaped such that the ascending and descending amount of the stitch cam with respect to the rotational amount of the driving motor is larger for a side for a larger drawing-in amount of knitting needles, while the ascending and descending amount of the stitch cam with respect to the rotational amount of the driving motor is smaller for a side for a smaller drawing-in amount of knitting needles.